Catalytic apparatus



Oct-.24, A. GIBB 2,

CATALYTIC APPARATUS I Filed Nov. 9, 1940 2 Sheets-Sheet 2 INVENTOR 2021w ATTORN Patented I '1 Lummus than of Delaware Company, New York, N.Y., a corpora- Application November 9, 1940, Serial No. 364,971

9 Claims.

This invention relates to improvements in pressure vessels particularlyof the shell and tube type suchas heat exchangers, catalyst chambers,and the likes i Catalytic reactions carried out in pressure vessels haveintroduced new problems of corrosion and erosion not only because ofthe'eflect of the high temperature of operation and of the substantialweight of the catalyst but also because the necessary heat exchange hasoften required that a molten material, usually a salt, be circulated inindirect contact with the catalyst to maintain it at a uniformtemperature; such ma terials are frequently highly corrosive. This isparticularly true in the'forms of heat controlling media used in thecontrol of the catalytic reactions of hydrocarbons as 'in the productionof superior qualities of gasoline;

'Iiieprincipalobject of my invention is to provide an improved form oftubular heat exchanger especially adaptedfor the carrying out ofcatalytic reactions,- in which the weight and cost of the equipment canbe greatly reduced without impairing the efiective life of the vessel orincreasing its maintenance.

It is a more particular object of my invention to provide a hightemperature, relativelyhi'gh pressure vessel having a substantial weightof supported tubular elements carried by a corrosion resistant and hightensile strength steel 'tube sheet, which in cross section has' a. formthat is initially a catenary so that there is substantially no bendingmoment placed in the tube sheet by the supported load and no resistanceagainst flexure is required.

A still further object of my invention is to provide a catalyst chamberof corrosion resistant, high tensile strength alloy steel having thecatalyst mass suspended substantially uniformly across a tube sheet ofthe same material, such tubesheet having marginal portions closelyfitting and coaxial with the chamber and welded thereto, the tube sheetbetween its edges being to the tube sheet and to the tube. Each of thesea surface of revolution of a. curve of initially catenary or modifiedparabolic shape so that all suspended loads are resolved to tensionloads in the tube sheet.

Another and more'particular object of the invention is to provide acatalyst chamber.- the in connection with the attached drawingsillustrative thereof, and in which Fig. lis an elevation, with partsbroken away, of an improved type-of catalyst chamber in accordance withmy invention; I

Fig. .2 is a. horizontal section taken substantially falong'the line 2of Fig. 1 showing the arrangement of the tubes and the expansionelereactions which are frequently carried out in the merits;

Fig. 3 is an" enlarged perspective view showing the manner of attachingthe tubes to each other and to the tube sheet;

Fig. 4 is a detailed vertical section taken on the line 4-4 of Fig. 2showing the manner'of securing the bottom to the catalyst-containingtubes; Fig. 5 is an enlarged detail showing the manner of attaching thetube sheet to the shell.

In accordance with the preferred form of my invention, I have shown aform of heat exchanger more particularly adapted for the catalytic re- 4action of hydrocarbons; such vessel is conveniently of the double walltype having an interior shell or liner l0 which is preferably of acorrosion resistant material such as stainless steel of the 18-8 varietyand is particularly adapted to'resist erosion and corrosion at therelatively high temperatures which exist in hydrocarbon temperaturerange of.1100 F. Preferably this shell I0 is cylindrical and it may besurmounted by truncated conical'top and bottom portions Illa and Nbrespectively.

Within such shell and in themain body portion there is a tubularstructure which is conveniently mounted in a vertical manner due to thenormal size of suchapparatus, such structure consisting of-a top orsupporting tube sheet I2 and a lower or secondary tube sheet I 4 and aplurality of tubes 18 and I1 supported thereby.

The manner of securing the tubes Hi to the tube sheet I 2 is moreparticularly shown in Fig. 3.

in which. it will be noted that the tube It extends through the tubesheet I! and is provided with a collar or a reinforcing flange it, whichis welded as shown in Fig. 4, is provided witha bottom which isdetachable, such -bottom consisting of a plate 20 which is convenientlybolted to the bottom extension "a of the tube by studs 2| havin nuts2la, which maybe of the acorn type to prevent destruction of thethreaded portions. It will be noted in Fig. 4 that the tube I6 extendssubstantially throughout the tube I1 and it maybe longitudinallyperforated.

The tube sheet l2, which forms the principal feature of myinvention,-i-s a surface of revolution and has a cross section which isinitially a catenary, which ultimately becomes a parabola. As shown inFig. 5, the edges of the tube sheet 12 are coaxial with and closely fitthe inner liner l near the top and are welded thereto. The tube sheet isthus suspended in shear but with the tube sheet in tension. A bar member23 preferably supplements the joint and adds to the rigidity of the tubesheet at its edge.

The tube sheet [2, when loaded, becomes parabolic in cross section,which is the shape of a flexible member supported on its ends and havinguniform loads suspended therefrom. The vertical loads imposed by therespective tubes l6 and 11, which are suspended therefrom in a uniformspacing, cause on reactionin the tube sheet except in tension. v

This construction is especially effective inasmuch as the use ofstainless steel of the 18-8' variety or other high tensile strength,non-corrosive materials can be used in relatively thin gauge with theminimum of weight for both the tube sheet as well as the inner liner ll]of the vessel. It will be understood that the tensile strength ofstainless steel is especially high, and,

as it is adequate in thin gauge to resist both corrosion and erosion,the thin gauge material meets all structural requirements and verysubstantially reduces the gross load of the vessel.

Catalytic reactions of hydrocarbons require substantial surfaces ofcatalyst, through which the vapors are conducted. In the presentinstance this is accomplished by introducing the 40 vapors throughv thenozzle 22 into the principal manifold or top-channel 24 with the vaporspassing into the respective tubes 16 and passing downwardly to thebottom of the tubes I1. Each of these tubes I1 is normally filled withthe desired catalyst with the result that the catalytic reaction takesplace during the emanation of the Vapors from the tubes l6 until thereacted prod nets are released from the top of the tubes l'l into theintermediate chamber 25. This is con-- veniently formed by thesupporting tube sheet l2 and the secondary tube sheet H. The secondary.

tube sheet II- also servesto space the tops of tubes H. The discharge'ofreacted products is through the nozzle 25.

The high temperature of reaction requires not only the most careful andcomplete insulation, which is accomplished by providing, insulatingmaterial 28 around the shell H), which *may be held in place by anexternal wall or cover 30, but means are provided for filling thechamber surrounding the catalyst reaction zone with a heat exchangingmedium such as molten salt of the desired temperature. The entire zonebelow the lower tube sheet I4 is thus maintained full of a a .hot andusually corrosive materialwhich is in- The means the fluid heatingmedium, and during the reactivation of the catalyst by oxidation, whichis an exothermic reaction, it is necessary to remove the heat by aid ofthe heat transfer medium without,

5 in either case, exceeding limiting temperatures which are required formaximum efficiency.

The normal high temperature conditions of operation are such thatsuitable expansion joints 35 and 36 are provided for changes in sizeduring expansion and contraction. It may also be desirable to providebailies such as 31 at suitable places transverse of the heat transfermedium zone for indirect flow and appropriate transfer of the fluidmedium between the inlet 32 and the outlet 33. Han'd-holes or cleanoutplugs 38 2 of apertures 40 in the inner liner Illa. They may also beprovided in the liner Ill in the region of chamber A practical andcharacteristic size apparatus of this type has an inside diameter of theliner of 25 ten feet and an overall height of twenty-five feet.

With such a construction the insulation is ap-' proximately 6" thick,and the top and bottom cones of the outer shell, which were of lowcarbon steel, were 1" and in thickness respectively.

The shell liner of 18-8 stainless steel, having a I tensile strength of95,000 pounds per square inch, was only f s'f in thickness with the toptube sheet l2 of ,5" and the lower tube sheet M of A" thickness. Thetube sheet I2 is deeply dished.

- A satisfactory depth for the sheet, prior to loading thereof, andmeasured along the vertical center line of the sheet from the bar 23 tothe sheet is one-fourth the diameter of the projected area of the sheet.

As originally designed; with the typical dished head constructionadapted to. support a catalyst load of approximately forty tons, theweight of the apparatus alone was approximately fifteen tons. By usingthe stainless steel, however, not

only in the liner but particularly in. the tube sheets, it was possibleto reduce the weight of the apparatus to approximately ten tons therebysaving over five tons of material. A large portion of the saving wouldhave been impossible even with stainless steel in the top tube sheet ofthe ordinary type as the moment of inertia of thin sections is so lowthat the customary beam would have been inordinately thick to resistflexure.

It will be appreciated that, in addition to static load oftubes. andcatalyst, the tube sheet has the additional, load due to the pressuredifferential which exists between the inlet channel 24 and the dischargechamber 25. This is inevitable in view of the passage of hydrocarbonsthrough the catalyst and in view of the very large diameters. A pressuredifferential of as little as fifteen pounds per square inch-will exert atremendous gross load, which also must be carried by the weldedconstruction of the upper tube sheet I! 'to the shell III. With thecatenary type of construction, no resistance to flexure had to be provided and the tensile strength could .be most effectively used, with theresulting thin gauge of material:

While I have shown and described a preferred form of embodiment of myinvention, I am aware that modifications may be made thereto and I,therefore, desire a broad interpretation of my invention within thescope and spirit of the desolve into substantially tensile ammoscription herein and of the claims appended hereinaiter. a

1. A pressure vessel, a plurality of vertically arranged catalyst tubestherein, vertically arranged tubes for admission of reactants to thecatalyst, means attaching the catalyst tubes to the said reactantadmission tubes, a deeply dished sub- 'zontal tube sheet ior saidadmission tubes with in the vessel and over the catalyst tubes, saidltantially horizontal tube sheet having when unloaded a catenarycross-section fixedly attached at its periphery to'the walls of saidpressure vessel, and means attaching said tube sheet to said walls, saidtube sheet being of such thickness and flexibility that the iull tubeload thereon will dethe catalyst, a deeply dished'substantially non tubesheet being of relatively thin high tensile strength corrosion resistantmetal and having when unloaded a .catenary cross-section, meansfixedlyattaching said tube sheet at the periphery thereof to the inner walls ofsaid vessel, and means interconnecting all 01' said tubing and said tubesheet for support of theload oi the tubing by suspension from the tubesheet, the

tube sheet being of such thickness and flexibility form said catenarycross-section into a parabolic l5 sheet.

2. A pressure vessel, a plurality of vertically arranged catalyst tubestherein, vertically arranged tubes for admission of reactants to thecatalyst; means attaching the catalyst tubes to cross-section so thatthe tube load will resolve into substantially tensile stress alone onsaid tube the said reactant admission tubes, a. deeply dished Isubstantially horizontal tube sheet having when unloaded a catenarycrossssection fixedly attached at its periphery to thewalls of saidpresto said walls, said tube sheet being of high tensure vessel, andmeans attaching said tube sheetsile strength corrosion resistant metaland being of such thickness and flexibility that the full tube loadthereon will deform said catenary'crosssection into a paraboliccross-section so that the substantially tensile stress alone on that thefull tube load thereon will deform said catenary cross-section into aparabolic crosssection so that the tube load will resolve into said tubesheet.

6. A reaction vessel, a plurality of vertically arranged parallelcatalyst tubes therein, vertically arranged tubes extending downwardlyinto said catalyst tubesfor admission of reactants to the catalyst, adeeply dished substantially horizontal' tube sheet for said reactantadinission tubes within the vessel and over the catalyst tubes,said-tubesheet having when unloaded a catenary cross-section, meansfixedly attaching said tube sheet at the periphery thereof to the innerwalls of said vessel, means interconnecting all of said tubing and saidtube sheet for suptube load will resolve into substantially tensile Istress alone on said tube sheet.

3. A pressure vessel, a'plurality or vertically arranged catalyst tubestherein, vertically arranged .tubes for admission of reactants. to thecatalyst, means attaching said catalyst tubes to the said reactantadmission tubes, a deeply dished sub stantially horizontal tube sheetfor said reactant admission tubes, said tube sheet having when unloadeda catenary cross-section, and means fixedly attaching said tube sheet atthe periphery thereof to the inner walls of said vessel, the saidreactant admission tubes being connected to said tube sheet for supportof the load of all of said tubing by the tube sheet and said tube sheetbeing of such thickness and flexibility that the full tube load thereonwill deform said catenary cross-section into a parabolic cross-sectionso that the tube alone on said tube sheet.

.4. .A reaction vessel, a plurality of vertically arranged parallelcatalyst tubes therein, verticallyarranged tubes extending downwardlyinto said catalyst tubes for admission of reactants to the catalyst, adeeply dished substantially horizontal tube sheet for said catalystadmission tubes within' the vessel and over thecatalyst tubes, said tubesheet having when unloaded a catenary cross-section, means fixedlyattaching said tube sheet at the periphery thereof tothe inner walls ofsaid vessel, and means interconnecting all of load will resolve intosubstantially tensile stress the catalyst tubes.

port of the load of'the tubing by suspension from the tube sheet, thetubesheet being 01' such thickness and flexibility that the full tubeload thereon will deform said catenarycrosssection into a paraboliccross-section so that the tube load will resolve into substantiallytensile stress alone on said tube sheet, and a second tube sheet withinthe vessel and spaced below the said first tube sheet, the first tube.sheet delimiting a reactant receiving space thereaboveand incommunication with the-reactant admission tubes, and the first andsecondtube sheets defining therebetween a vapor receiving space incommunication with the upper ends of 7. A-reaction vessel, a pluralityof vertically arranged parallel catalyst tubes therein, verticallyarranged tubes extending downwardly into said catalyst tubes foradmission of reactants to the catalyst, a deeply dished substantiallyhorizontal tube sheet for said reactant admission 7 ,tubes within thevessel and over the catalyst tubes, said tube sheet having when unloadeda' catenary cross-section, means fixedly attaching said tube sheet atthe periphery thereof to the said tubing and said tube sheet for supportof the load'oi the tubing by suspension from the tube sheet, the tubesheet beingv of such thickness and flexibility that the full tube loadthereon will deform said catenary cross-section into a paraboliccross-section so that the tube load will re- ,stress alone on said tubesheet.

5. A reaction vessel, a plurality of vertically arranged parallelcatalyst tubes therein. vertically arranged tubes extending downwardlyinto said catalysttubes for admission of reactants to aotantreceivingspace thereabove and incom-,

munication with the reactant admission tubes.

- the first and second tube sheets defining, therebetween avapor-receiving space in communication with-the upper ends of thecatalyst tubes, and the second tube sheet delimiting a spacetherebeneath for a heat exchange medium to surround the catalyst tubes.

8. A reaction vessel, means for eflfecting contact of reactants and acatalyst within said vessel tially horizontal tube sheet for the upperend portions of said tubes, said tube seet having when unloaded acatenary cross-section, means fixedly attaching said tube sheet at theperiphery thereof to the inner .walls of said vessel, and means toimpose upon said tube sheet, in distribution over the area thereof, thecombined weight of said tubes and of a quantity of the catalyst, saidtube sheet being of such thickness and flexibility that said weight willdeform said catenary cross-section intoa parabolic cross-section so thatsaid weight will resolve into substantially tensile stress alone uponthe tube sheet.

9. The method of supporting a load of catalyst tubing and associatedreactant admission tubing from a tube sheet for said reactantadmissiontubing within a reaction vessel, which method comprises forming aflexible plate into a deeply dished form having a catenary cross-sectionwhen unloaded and deformable by said load to a parabolic cross-section,fixedly attaching the tube sheet at the periphery thereof to the wallsof the vessel, distributing said load horizontally and substantiallyevenly over the vertically pro- JOHN A. GIBB.

